Mousefood – Build embedded terminal UIs for microcontrollers
(github.com)242 points by orhunp_ 4 days ago
242 points by orhunp_ 4 days ago
Sure, but that's beside the point.
Text based graphics with fancy or custom fonts is just crazy efficient. That is exactly how we got the amazing graphics of The Last Ninja or Turrican on machines with less than 64KiB useable RAM.
Same for more modern embedded devices. If you constrain yourself to text you increase both runtime performance and your developer productivity.
The same isn't true for modern embedded devices, they don't have tile rendering hardware. If you connect a i2c/SPI screen (SSD1306, ST7735), you write all the pixels on the screen (or pixels to some subregion of the screen), these screens do have a backing memory in them.
So in order to draw a line, you will - objectively - have to copy/move more bytes if you approximate line with character symbols.
This isn't a big deal, but crazy efficient it is not.
All the efficiency when drawing on those screens mostly relies on how well you chain together DMA transfers to portions of the screen you want stuff to be drawn to, so that SPI transfers aren't blocking the CPU (that's assuming you don't have memory for a second full-screen buffer).
SSD1306 is a bit in the middle. It's technically a 128x64 monochrome bitmapped display, but it's organized as eight 128x8 "rows", with each byte representing a single 1x8 group of pixels. That organization really favors being treated as either four or eight lines of text - trying to use it as a generic bitmap display gets awkward, because it's only addressable at the level of those 1x8 groups.
ST7735 is more of a standard (color) bitmap display.
SSD1306 is just 1KByte for a second buffer, so even a rather low-end MCU likely can spare that. And you'd absolutely just draw normal lines if you use a display like that.
It's very easy to use it as a generic bitmap display, there's nothing awkward about packing 8pixels into 1 byte, and you can set the addressing mode (horizontal/vertial) to whatever you want, etc.
It was crazy efficient on character or tile-based hardware. It makes no difference on bitmap displays, or rather adds some overhead.
At the end of the day it's always pixels - alway has been [1] - and the efficiency of storing and blitting a small number of fixed size rectangles is hard to beat if you can get away with it.
[1] Except for the early oscilloscope style vector displays maybe.
For simple SPI displays it's the transfer bandwidth that dominates, so for best performance you wanna minimize the number of pixels you need to send. So for eaxmple: if you wanna draw a 100 pixel long horizontal line, if you ever send more than 100 pixels of data you're not gonna hit the speed of light. And if you wanna draw an angled line you're gonna have to do something like bresenham and pixel by pixel because drawing NxN blocks for a 45 degree line would be insane.
Hey all, thanks for the interest to the crate!
I'm currently live on YouTube (doing some maintenance & testing). Feel free to join if you have any questions!
My experience is with Aruduino wiring vs Rust with embassy. And very much from a hobbyist POV.
Rust on embedded uses a HAL layer, which is vendor independent (and resolved at compile time, like templates would be in C++). It doesnt cover everything yet, but basics like GPIO, SPI, I2C etc are covered. This avoids the issue of N drivers times M vendor SDKs: I2C drivers can just be written against the HAL, and you instantiate with a specific HAL in your application. Also reduces vendor lock-in. The setup process still requires some chip specific code to select which pins to use etc, but once you are past that you can be vendor neutral.
Speaking of which, the API uses some clever patterns (called typestate) to ensure at compile time that your peripheral config is valid: if you "take" GPIO2 you can do that again, so you can't give the same pin to two different pieces of code by mistake. And if the driver expects a pin configured as output you can't give an input pin (you can convert a pin to "dynamic at runtime" if you really need to, so there is an escape hatch).
Then there is the embassy framework. This is an alternative to RTOSes (there are some Rust RTOSes as well, haven't tried them). It makes use of async/await tasks in Rust that are statically allocated and scheduled. You can have several priority levels of schedulers (even though internally the schedulers are cooperative for the tasks inside, but they are preempting between schedulers by using interrupts).
Async actually makes many things on embedded easier, such as waiting for a GPIO. No longer do you need to write your own interrupt handler, or figure out when to put the chip on a low power state, the scheduler and HAL futures do it for you.
All that said: C++ still is a larger ecosystem with more tutorials, drivers and better chip support. But that is advancing rapidly in the Rust world. ESP32 series has official vendor support in Rust for example, as does at least one or two other vendors (or they are in the process of adding it). Popular chips like the RP2040 etc have support, and I have seen HALs for NRF and ST around (but never played with them). Drivers for common chips exist.
So I would say it is worth experimenting with at least, but you should check up front what HALs and drivers exist for what you want to use and check how complete those are. Two years ago I wanted to do I2S things on the ESP32, but that was still missing. A year ago it had support, but some of the DMA things were clunky still. I should check again some time.
ComputerCraft was part of how I learned to code.
I first learned about password hashing when I tried to make the actually most secure door lock program. I first used raw SHA-256, but then someone on the forum introduced me to PBKDF2...
Sometimes I miss those days.
This is awesome! I love ratatui, having it available on embedded is very cool! I wonder if it will work with async on embedded e.g. embassy..
Most likely. I just checked and it uses embedded-graphics already which means you can plug in Mousefood directly. The touchscreen might be a bit tricky though, it might need some hacking on the event handler side. But it will most likely work if you map the coordinates to the terminal cells abstraction somehow.
Today I Learned: https://github.com/witnessmenow/ESP32-Cheap-Yellow-Display
fwiw, in my research into this, it looks like there are inconsistencies in the devices available, since there's no one manufacturer and they're clones of clones. one might have been reliable but then it goes out of stock
aaaaand this how I learn rust I learned go because of bubbletea and mousefood (which combines my work as an embedded systems programmer and love for torminals) is here
Oh bubbletea is really cool. Is this how most interactive CLIs are made?
I used bubbletea for a while but quit it because of inconsistencies in the design. Went to ratatui and never looked back. Go and Bubbletea are nice, but rust is much more suited for building tuis.
> Embedded-graphics includes bitmap fonts that have a very limited set of characters to save space (ASCII, ISO 8859 or JIS X0201). This makes it impossible to draw most of Ratatui's widgets, which heavily use box-drawing glyphs, Braille, and other special characters
You have a bitmap display, you can just draw lines and stuff without needing to rely on font-based hacks.